The Great 3F build off

allanferguson
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Re: The Great 3F build off

Postby allanferguson » Wed Jul 11, 2012 2:41 pm

I'm enjoying your build of the CR 812, not least because I'm building one concurrently. A couple of points have emerged re the tender, which may be helpful.

First, the position of the brake standard is not described in the instructions, nor shown in any of the pictures in the book. So my best guess is a copy of other people's models, plus intelligent inference. I even spent time on the footplate of 828 in Boat of Garten, and failed to get this information!

Secondly the buffers are designed to be secured by a nut at the back, and a slot is etched in the cosmetic outer frames to leave room for the nut. However, this leaves virtually no room for the nut to move, and it is impossible to enlarge the slot with everything assembled. I've settled for unsprung buffers.

Allan F

812 tender 1.JPG


812 tender 3.JPG

David Knight
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Re: The Great 3F build off

Postby David Knight » Wed Jul 11, 2012 4:08 pm

Hi Allan,

Glad this effort is of some help. I seem to recall something in the instructions about the brake standard and the positioning of the box top with the hole etched in it and at least one photo confirmed the location so there you are. My brake standard went in the same spot as yours so we must be right :thumb

My buffers are the standard Gibson, Drummond LSWR ref 4910 round base type that have the .5 mm tail that needs a collar or can be bent to secure. I suppose it depends on the vintage of the kit, mine was bought in (I think) the late '90s. At any rate they have enough room to work but I'll wait until the paint shop is finished before I add the heads.

Did you get the tool box location from your experience on 828? if so that is very helpful and I can do mine in the same location.

Cheers,

David

allanferguson
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Re: The Great 3F build off

Postby allanferguson » Wed Jul 11, 2012 5:58 pm

David

My tender kit was bought fairly recently, and had the Slaters (I think) Drummond buffers as shown.

The toolbox position is as on 828, as in the book, as in every photograph I've seen, and as on the Caley Association drawing for the 3000 gal tender. Good enough for me! Just shows the danger of going from Works drawings.

Incidentally are you going to fit, or have you fitted, the boiler bands provided? My received wisdom at the moment is that all etched boiler bands are much too thick.

Allan F

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Jim Summers
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Re: The Great 3F build off

Postby Jim Summers » Wed Jul 11, 2012 7:08 pm

Keep the bands off, I'd say.
Here is mine, and you can see the way I did the tender. It is an old photo. The tender and loco have a fallplate now.

JIm
Attachments
828 test shot with Canon.JPG

David Knight
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Re: The Great 3F build off

Postby David Knight » Wed Jul 11, 2012 9:41 pm

Thanks for the information Allan, one more bit to be added.

I'm going to use sellotape type tape for the boiler bands as per the advice of Chris Gibbon who recommends it for his kits.

Thanks for the pic Jim, you've shown the job can be done. Any advice for the cab/tender doors that can be seen hanging open in most pictures? I'm thinking a bit of fret waste will serve but the fastening is a small puzzle.

Cheers,

David

David Knight
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Re: The Great 3F build off

Postby David Knight » Fri Jul 13, 2012 1:01 am

As previously mentioned the engine frame is next. I'm using the Roger Wyatt 3 axle spreadsheet from the CLAG site and have derived the following values for a 31mm x 36mm wheelbase;
A-P 13.5, Q-B16.5, Q-C 17.5, R-D 10 giving deflections of; y1=0.6542, y2=0.5089 and y3=0.6550 This was done using the values already on the chart for wire size and weight distribution as they seemed reasonable for my engine. As this is the first engine I've CSBed on my own does anyone have any helpful comments?

Cheers,

David

Alan Turner
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Re: The Great 3F build off

Postby Alan Turner » Fri Jul 13, 2012 8:36 am

You can't physicaly have different deflections of the axles - what your calculation is actualy telling you is that the centre axle is carrying more load than the two outer axles, in other words your chosen weight distribution does not tally with the actual distribution.

In fact the weight distribution is: 32.49% - 35.36% - 32.18%. The centre of action is also forward - tending to nose heavy.

If you adopt : A-P 12, Q-B16.5, Q-C 17.5, R-D 9 Your load distribution becomes: 33.49% - 32.97% - 33.55% which is both more balanced and the centre axle is a little softer ensuring the chassis dosen't have a tendency to rock.

regards

Alan
CSB.PNG

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Russ Elliott
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Re: The Great 3F build off

Postby Russ Elliott » Fri Jul 13, 2012 9:09 am

David - there's too much weight on your middle axle. The objective is to have an equal or slightly lesser weight on the middle axle. (To prevent porposing.) When playing around with the fulcrum positions on Roger's/Will's spreadsheet, you therefore always want to get the middle axle deflection to be equal or greater than the outer two, ensuring that when in reality they are all equally deflected, there is slightly less weight on the middle axle. Alan's spreadsheet is very useful if you want to finesse the axleweights.

Try A-P 14, Q-B 16.5, Q-C 20.5, R-D 12

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Will L
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Re: The Great 3F build off

Postby Will L » Fri Jul 13, 2012 9:25 am

David

I agree with Alan and Russ, you suggestion has too much weight on the centre axle.

While this tends to be traditionalist hobby, Roger's original spread sheet is the hardest to drive, I think it is worth getting to grips with either of the other two spread sheets on the CLAG, either Alans or mine, as it is clearer what you are up to. Despite doing the job two different ways they all give the same answers.

This prototype is actually quite tricky because it is significantly asymmetric.

Both Alan and Russ's plots are good and I shan't confuse things by adding another. So chose one and unless they puts a fulcrum point some where you would rather it wasn't, that will be OK.

A bit of additional info.
The centre of gravity should offset be 1.5mm from the centre axle towards the distant axle.
The wire size you will require is given by the following table so you can select the right wire when you know the loco weight. Use the value closest to your actual loco weight
Alan's plot
loco weight (gms) - 340, 250, 190, 135
wire size (thou) ----- 15 , 14 , 13 , 12

Russ' plot
loco weight (gms) - 360, 280, 210, 160
wire size (thou) ----- 16 , 15 , 14 , 13

You will note that Russ's plot is a bit softer than Alan's so you need a thicker wire for a similar loco weight. What is a good thing here is not clear.


Will

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Russ Elliott
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Re: The Great 3F build off

Postby Russ Elliott » Fri Jul 13, 2012 10:37 am

Will - I wrote my post before I saw Alan's, and I didn't mean to infer that his plot was any less valid, so my suggested values (which will give equally weighted axles as near as dammit) can be seen as merely an alternative possibility (of which there are many of course). Longer spans do however help reduce the errors in fulcrum positioning and widths, but having said that, the longer spans might be more difficult for David's overall frame length (particularly at the front end?), and David's final choice will depend on the convenience of the fulcrum placements.

Alan Turner
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Re: The Great 3F build off

Postby Alan Turner » Fri Jul 13, 2012 11:15 am

This is Russ's dimensions reproduced in my spreadsheet. As you can see, as Will says, softer set up but at the expence of needing 14mm in front of the front axle.

regards

Alan
CSB mk2.PNG

David Knight
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Re: The Great 3F build off

Postby David Knight » Fri Jul 13, 2012 1:37 pm

Gentlemen,

Many thanks for your input. I had a suspicion all was not correct and this has been confirmed. My main reason for not using Alan's spreadsheet was I couldn't read it on my Mac for some unknown reason. That said I think I will be using Alan's plot as I only have 12mm from the rear axle centre to the drag beam and Russ' plot won't fit!

Cheers,

David

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Will L
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Re: The Great 3F build off

Postby Will L » Fri Jul 13, 2012 9:18 pm

Russ Elliott wrote:Will - I wrote my post before I saw Alan's, and I didn't mean to infer that his plot was any less valid...

And I don't think you did. As you say, several (many) different plots are usually available. Each will have slightly different characteristics, but deciding which is best is more a matter off circumstance and personally preference that anything concrete. That said you had both came up with what I thought were better balanced plots than I had.

Will

David Knight
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Re: The Great 3F build off

Postby David Knight » Sat Jul 21, 2012 6:41 pm

After having bravely said that I was moving on to the frame I have to back up a bit. My book on 828, (Caley 828, Jim MacIntosh, Caledonian Railway Association) arrived with a wealth of pictures (excellent book!) and I had a look through another book Steam In Scotland, Vol. 1, W.J.V. Anderson & Derek Cross, Ian Allen which has a few additional pictures of the class. As far as the tenders go there seems to be an additional bulkhead between the coal and the water filler caps appearing on many engines and then there is the question of patches on the lower part of the tender sides. Some of the patches seem to be a late BR application others seem to date from LMS days so more sniffing about is needed there. In addition some engines have dogs added to the smoke box doors, once again a BR thing but the question is when? Most engines with the dogs applied have the late BR crest so I may just apply the early one (as I had planned anyway) and skip the dogs but if anyone has some inside info it would be appreciated. I have narrowed down my choice of engine to ones with steam brake only so this should help a little along with a preference for Sou'West lines. I know, it would be much easier if I had a specific engine to start with but I was transported to Canada at an early age and by the time I got back the 812s were all gone.

Cheers,

David

David Knight
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Re: The Great 3F build off

Postby David Knight » Sat Aug 18, 2012 12:42 am

It's been a while since the last post so I thought I'd bring you up to speed on the progress or lack thereof. I've finally settled on a particular engine that being 57572 which lands in the right geographic area, is steam brake only and I have at least one decent picture to help with the details. I've started on the frame with the cutouts for the bearings done, handrail knobs fitted for the CSBs and the spacers installed. I've added an additional bulkhead to the top of the tender between the coal board and the water fillers and fitted the toolbox. There is still much to do on the tender as I need to add patches to the sides and rear end and an additional handrail and a pair of steps. I've selected a gearbox, the HighLevel Loadhauler (54:1) and am looking at ways to rig it with a suitable tourque reaction link. At the moment it looks like I'll be using a Mashima 1220 set up vertically in the firebox but that may change. Once I have some pics I'll post them.

One last thing, the smokebox door probably had additional dogs fitted around the circumference in order to get a better seal. The kit does not contain any castings/etchings or suggestions for modelling this feature. Does anyone have any suggestions (apart from the "it's your trainset" one)?

Cheers,

David

David Knight
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Re: The Great 3F build off

Postby David Knight » Tue Aug 21, 2012 1:15 am

Back again with the pics. First off the tender showing the additional bulkhead (correct terminology?) and the water filler lids in position. I know I said I was going to turn up a set but a little fettling sorted the problem and any eccentricity will not be visible to the casual observer.
tender.jpg
tender.jpg (102.03 KiB) Viewed 7281 times

Next the frame with CSBs strung and the footplate and gearbox fitted.
frame and gearbox.jpg
frame and gearbox.jpg (106.15 KiB) Viewed 7281 times

The need for the extended box becomes obvious once the footplate is placed on top as otherwise the cab would be in the way of the motor.
temporary fit.jpg
temporary fit.jpg (95.38 KiB) Viewed 7281 times

Next up will be fitting the wheels which will require a jig as the crankpin holes are only dimpled and I'd rather like all wheels to have the same throw.

Cheers,

David

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Jol Wilkinson
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Re: The Great 3F build off

Postby Jol Wilkinson » Tue Aug 21, 2012 7:44 am

I realise that High Level motor mounts are the preferred product of choice nowadays, but I find that a single stage "simple" arrangement such as provided by a London Road Models motor mount and Mashima motor in an "underslung" position can provide plenty of clearance in small or medium size pre-group locos. I think that this approach also makes it easier to get the motor into the firebox, than having a horizontal motor located in the boiler.

CT frames 2.JPG
LNWR Coal Tank with Mashima 1224 and 38:1 gears


Precursor frames 2.JPG
LNWR Precursor with Mashima 1426 and 50:1 gears


I've used this arrangement in nearly every P4 loco I have built - the notable exception being a Portescap 1624 with MJT conversion that sound as though it is turbocharged. The only other one that has proved less than satisfactory is a 1420 in an 0-8-0 which is noisy in one direction only (forwards, of course). I am unsure whether this is down to the motor or gears, so it is about to get a rebuild, replacing both.

Jol

David Knight
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Re: The Great 3F build off

Postby David Knight » Sun Aug 26, 2012 8:51 pm

As mentioned previously the Gibson wheels for the 812 class (among others) come with a dimple but not a hole where the crankpin should be. Some time ago there was discussion on one forum or another about the importance of getting all the crankpins with the same throw if smooth running is ever to be attained. Here is my take on a solution.
the bits.jpg

The bits are quite simple, a turned bearing holder with a spigot that is a close sliding fit in the Gibson wheel, in this case it measured out at 3mm for a 1/8" axle. A long Gibson crankpin bearing completes the needed bits. The bearing holder is 10 mm in diameter by 2 mm thick with the spigot 3 mm thick by 3 mm diameter. The centre is drilled out 0.7 mm as a reference point for measuring the crankpin throw. The throw can be determined from works drawings and converted or you can measure from the centre of the wheel using the spigot hole & a vernier calliper or dividers to the dimple in the wheel. The resulting measurement and centre finder can be used to transfer the dimension to the face of the jig and a hole drilled to take the Gibson bearing which is 1.5 mm in diameter.
Jig in use.jpg

The picture should be self explanatory, but here goes; carefully position the jig without the bearing over the hub and spot through to the dimple, you can also use the spokes (or the space between depending on the placement) as guidance. Clamp the jig in place, drop in the bearing and drill through the hub with a #70 drill as prescribed by the Gibson instruction sheet. Once completed you can either run a crankpin screw through the hole or a 14BA tap if you are fastidious, countersink the hole on the back side for the screw head. Repeat for the remaining wheels. Enjoy! ;)

Jol,
Your point is well taken and I certainly would not consider my methods of gearing to be gospel, the thing is, I've had the gearbox "maturing" for about the same time as the kit and thought it about time that it earned its keep ;) . It does also fit rather well in this configuration especially for the torque reaction link placement which comes next.

Cheers,

David

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Mike Garwood
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Re: The Great 3F build off

Postby Mike Garwood » Mon Aug 27, 2012 11:10 am

David

Love the solution to a time old problem. What diameter exactly did you settle on for the main 'spigot' that goes into the wheel boss? I ask this as I have had a go at a similar solution but without the aid of a lathe, I used one eighth brass as the main spigot and it seemed to open out the wheels and took a bit of their grip away, when they went onto the axle.

Enjoying the build...of both.

Mike

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Russ Elliott
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Re: The Great 3F build off

Postby Russ Elliott » Mon Aug 27, 2012 11:36 am

Mike - suggest run your bit of eighth brass in a drill and take off a smidge with a file or some wet'n'dry. It will probably end up a bit tapered, but that will help it keep a snug fit in the wheel axlebore without distorting it unduly.

David Knight
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Re: The Great 3F build off

Postby David Knight » Mon Aug 27, 2012 1:41 pm

Mike,

I just had a quick measure and the spigot came out at 3.09 mm or 0.1215". I used a series of tries with numbered drill shanks to get the starting point and settled on a sliding fit so as to avoid stretching the wheel centre, the knowledge that I had the mini parallel clamps also helped. I got the idea, IIRC, from a discussion in which Dave Booth figured prominently but never had the occasion to try it out until now.

Cheers,

David

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Horsetan
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Re: The Great 3F build off

Postby Horsetan » Mon Aug 27, 2012 5:56 pm

Mike Garwood wrote:David

Love the solution to a time old problem. ....


And it could pave the way to making and marketing a series of such jigs. Useful also if you have a wheel where you want to put in a different crank throw, e.g. AGW's BR 5' wheel which has a 24" throw as standard for the Class 2s, but which could be re-drilled for 28" for use on a 9F.
That would be an ecumenical matter.

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grovenor-2685
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Re: The Great 3F build off

Postby grovenor-2685 » Mon Aug 27, 2012 6:50 pm

a series of such jigs.
No need for a series, one jig has room for a lot of crankpin holes ;)
Keith

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Horsetan
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Re: The Great 3F build off

Postby Horsetan » Mon Aug 27, 2012 8:06 pm

grovenor-2685 wrote:
a series of such jigs.
No need for a series, one jig has room for a lot of crankpin holes ;)


Please let me finish:

...or a jig with a series of crankpin holes..... :mrgreen:
That would be an ecumenical matter.

David Knight
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Re: The Great 3F build off

Postby David Knight » Mon Aug 27, 2012 8:31 pm

Horsetan wrote:or a jig with a series of crankpin holes..... :mrgreen:


I fully intend to use mine for more than just the one project as I have a Terrier in waiting with undrilled holes plus I think the jig will be useful even for the mundane task of setting the crankpin screws in place on wheels with pre drilled holes as there is a better chance of getting things square.

I have another simple jig to help press axles on square but I have a few holes to drill first... :D

Cheers,

David


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